The present invention relates to an improvement in an oil control valve (hereinafter referred to as OCV) for controlling a variable valve timing gear of an internal combustion engine and an installing method thereof.
In the internal combustion engine, particularly in 4-cycle gasoline engine for vehicles, valve timing of at least one of intake and exhaust valves is controlled in order to improve performance of the engine. In a method generally employed for controlling the valve timing, a rotational phase with respect to a crankshaft of a so-called over head camshaft (hereinafter referred to as an OHC) mounted on an upper portion of the engine is hydraulically controlled by a variable valve timing gear (VVT) mounted on a shaft end of the OHC.
A valve that supplies a controlled hydraulic pressure to this VVT is the oil control valve (OCV).
In general, the OCV is a valve drive with a solenoid coil, which is installed in the vicinity of a bearing of the OHC of a cylinder head in order to form a hydraulic oil line on a wall of the cylinder head thereby shortening the hydraulic oil line.
FIGS. 13 and 14 show an OCV installed in an engine disclosed in the Japanese Patent Publication (unexamined) No. 280541/1999, for example. FIG. 13 is a view taken from a front part of the engine, and FIG. 14 is a view taken from an upper part of the engine.
In the drawings, reference numeral 1 is a cylinder head, numeral 18 is a cylinder head cover (hereinafter simply referred to as head cover) mounted on an upper portion of the cylinder head 1, numeral 5X is an intake camshaft disposed on the upper portion of the cylinder head 1, numeral 6 is an exhaust camshaft disposed in the same manner, numeral 14 is bearings (also called cam caps) rotatably holding the intake camshaft 5X and the exhaust camshaft 6.
Numeral 20 is a variable valve timing gear attached to one end of each camshaft 5X, 6, and numeral 30 is an oil control valve that supplies a controlled hydraulic pressure not shown to the variable valve timing gear 20. The oil control valve 30 is mounted on the cylinder head 1 by a fitting bolt 54, with an O-ring member 55 held between the oil control valve 30 and the cylinder head 1. Numeral 56 is an oil filter, and numeral 50 is a chain guide.
FIG. 15 is a detailed enlarged view showing the construction of the oil control valve OCV 30 in FIGS. 13 and 14. In the drawing, numeral 2 is an OCV installation hole provided in the cylinder head 1, and the OCV installation hole 2 has plural hydraulic oil lines 2a to 2e. Numeral 2a and 2c are drain lines, numeral 2b is an oil supply line, and numeral 2d and 2e are oil lines communicating to the variable valve timing gear 20.
Now, operation of the mentioned known art is described.
Numeral 3 is a housing inserted into the OCV installation hole 2, and plural partition walls are provided in the housing 3. Numeral 5 is a spool type valve that is inserted into the housing 3 and moves in axial direction according to whether or not a solenoid 31 is energized, and the spool type valve 5 is in contact with a drive shaft of the solenoid 31 by an urging force of a spring 4. As shown in the drawing, plural hydraulic oil lines are provided, and when the solenoid 31 is not energized, oil is supplied from the oil line 2b to 2d, oil in the oil line 2e is discharged to the oil line 2c, and a phase angle of the variable valve timing gear 20 is changed. On the other hand, when the solenoid 31 is energized, oil is supplied from the oil line 2b to the oil line 2e, oil in the oil line 2d is discharged to the 2a, the phase angle of the variable valve timing gear 20 is changed in a direction opposite to the foregoing direction. In the neutral state, oil supply from 2b to 2d and 2e is interrupted, oil discharge from 2d to 2a and from 2e to 2c is interrupted, and the phase angle of the variable valve timing gear 20 is held as it is.
Numeral 32 is a connector for energizing (applying a current to) the solenoid 31, and numeral 33 is a metal case forming a part of a magnetic circuit of the solenoid 31.
In order to prevent oil from leaking outside through an opening between a wall face of the OCV installation hole 2 and the housing 3, a first O-ring 54a is disposed between the wall face of the OCV installation hole 2 and the housing 3. A second O-ring 54b is disposed in order to prevent oil from leaking outside through an opening between the housing 3 and the case 33, and third O-rings 54c and 54d are disposed in order to prevent oil from leaking outside of the solenoid 31.
As shown in FIGS. 13 to 15, the OCV 30 has its oil line-switching portion (the housing 3 and the spool type valve 5) in the engine, but it is inevitable that the solenoid 31 and the connector 32 of the OVC 30 are disposed outside the engine for convenience of wiring.
As described above, the conventional oil control valve is installed with its solenoid portion protruding from an outer wall of the engine, and this worsens a space factor in engine room. Moreover, it is necessary to provide many oil lines in the cylinder head because of its installation structure.
The present invention was made to solve the above-discussed problems, and has an object of achieving an oil control valve in which the oil control valve protrudes less from the engine, has less oil lines, and has less oil leaks. Another object of the invention is to provide an installing method of such an oil control valve.
One object of the present invention is to achieve an oil control valve in which the oil control valve protrudes less from the engine, has less oil lines, and has less oil leaks. Another object of the invention is to provide an installing method of such an oil control valve.
An oil control valve according to the invention is to control a variable valve timing gear for adjusting operation timing of at least one of exhaust and intake camshafts mounted on a cylinder head of an internal combustion engine, and include a housing provided with plural oil lines and a spool type valve that moves in the mentioned housing to open and close the oil lines; and a solenoid having a metal case that forms a part of a magnetic circuit and driving the spool type valve.
And the housing is mounted on the cylinder head of the internal combustion engine, and at least a part of the metal case passing through a through hole provided through a cylinder head cover covering the cylinder head is disposed outside the cylinder head cover.
As a result of employing such a construction, even in case of oil leakage in the OCV, the oil leaks only within the cylinder head cover and does not leak outside, and therefore it is possible to simplify the structure of preventing oil from leaking outside the oil control valve.
And the housing is mounted on the cylinder head of the internal combustion engine, and at least a part of the metal case passing through a through hole provided through a cylinder head cover covering the cylinder head is disposed outside the cylinder head cover.
As a result of employing such a construction, even in case of oil leakage in the OCV, the oil leaks only within the cylinder head cover and does not leak outside, and therefore it is possible to simplify the structure of preventing oil from leaking outside the oil control valve.